I know you read TVTropes with the reference to the Proud Warrior Race Guy :) so you'll know it's a Planet Of The Hats type situation.

This sort of thing comes from trying to extrapolate an entire culture based on one or two insignificant facts gleaned from a minor role in the source material. With one or two supporting characters to go by, writers assume that they are typical for their species, and use them as a model for the rest, whilst being unwilling to go against what they perceive as the official canon version. They're afraid to invent anything new, particularly when it comes to somebody else's creation (ie George Lucas's).

Jabba is a gangster, so all Hutts become gangsters. Bothan spies stole the Death Star plans, so all Bothans become spies. Bib Fortuna was a gangster's henchmen, so all male Twi'leks become gangster types, whilst that Twi'lek dancer of Jabba's became the model for all the female Twi'leks. And so on, and on, and on.

Yes, I know it's a planet of hats situation.  But Star Wars seems to push the Planet of Hats trope far more than other sci-fi universes, to the point of a 'genetic predisposition' to become slave dancers.  Which is enough to get me ranting, why was that even needed or beneficial? Somebody in a multi-billion dollar empire really thought adding a slave dancer gene was a good idea and an executive okayed it?
Heck, even the races created for the EU seem to have remarkable genetic predispositions, are there any non-assassin Noghri?

I was just leafing through a Clone Wars comic and came across a section where Ayla Secura mentions that Twi'Lek females have a genetic disposition to become slave dancers. . . unbelievable.

Female Twi'leks have been considered especially attractive and slender, which made them favorite subjects for slavery and entertainment. The beauty of female Twi'leks was well known throughout the galaxy, and as a result many nubile ones were sold into slavery, becoming dancers or status symbols, most notably by Jabba Desilijic Tiure, while the usual ugliness of the males was also well known.

You think that's bad? Zeltrons are an entire race of prostitutes, except for the one mechanic who's a main character!

Why? Because they're naturally and permanantly empathic, so what better way to make sure you're life isn't hell than to make everyone else happy?

Who's brilliant idea was that?

Besides, you can throw things like that around as much as you like, since you're all guilty of it.

After all, everyone knows that all Gungans are like Jar Jar Binks...

I would think definitions on what constitutes a waste of a talent would be dependant upon the person taking it or the person writing said character for the tv show.

Not everything you do for your character has to be done to maximize your character potential or minimize their flaws. Some things are done for... gasp... flavor.